Running a biodiversity net gain assessment - calculating BNG

What exactly is the Biodiversity Metric?

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Read more about the Statutory Metric sheet.

Find out if BNG applies to your development and get all the information you need!

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Calculate your BNG

• grassland 
• hedgerows 
• lakes
• woodland 
• watercourses such as rivers and streams 

• The number of biodiversity units are there before development starts
• The number of new biodiversity units that you need, to replace the units lost and achieve 10% BNG.

Who should use and understand the Biodiversity Metric sheet?

• Property Developers creating a biodiversity gain plan
• Local Planning Authorities who are interpreting metric outputs in a planning application
• Landowners, homeowners or land managers who want to provide biodiversity units from their sites to others
• Communities who want to understand the impact of a local development

1. Homes:
   • 1 to 9 houses on land up to 1 hectare
   • Or, if the number of houses is unknown, land less than 0.5 hectares
2. Business buildings:
   • New space less than 1,000 square metres
   • Or total land less than 1 hectare
3. Not allowed for:
   • Mining
   • Waste management.

Find out if you are exempt from BNG

Find out if BNG applies to your development and get all the information you need!

Use the exemption checker

What information do I need for the metric tool?

• the types of habitat, both present and planned  
• the size of each ‘habitat parcel’ in hectares or metres squared, or for linear habitats (watercourse and hedgerows) in kilometres or metres
• the condition of each ‘habitat parcel’ 
• photographs of each habitat parcel
• (in the future} whether the proposed actions for the habitat parcel are mapped in the local nature recovery strategies local habitat map (in draft) or identified in other alternative strategies.

What documents do I need to calculate BNG?

• Either the Statutory Metric sheet or the Small Site Metric sheet
• A Biodiversity Net Gain Plan
• And a habitat plan. 

Measure your Biodiversity Net Gain and comply with the law.

The Biodiversity Net Gain Tool offers small sites end-to-end compliance with the new BNG law.

Use the tool today

More information for developers and architects.

• Choose someone competent to do the site survey and fill in the metric (the “competent person”). The statutory metric must be done by a suitably qualified ecologist. An ecologist is not needed for the Small Site Metric (SSM).
  
• Complete a biodiversity metric sheet (or an SSM sheet) showing the baseline habitats. This should be based on a site survey. They should also think about how they will assess the development afterwards.
• Use the sheet to work out the biodiversity value of the habitat before development starts.
• State whether any activities (such as building over habitat) have resulted in a loss of on-site biodiversity value. If so, they must provide more information.
• Describe any irreplaceable habitats.
• Show the on-site habitat as it was on the date of application (or earlier proposed date), including any irreplaceable habitats.
• Follow the instructions in the user guide and Schedule 7A of the Town and Country Planning Act.
• The applicant should also think about any other rules their local planning authority (LPA) has in addition to the mandatory Biodiversity Net Gain.

1. calculated the number of biodiversity units (thus, biodiversity value) the site has
   
2. the biodiversity loss through development
3. what you need to do to achieve 10% biodiversity net gain.

More information for land owners and managers.

More information for LPAs.

• Statements by the applicant:
  
  • Whether the planning permission, if granted, would be subject to the biodiversity gain condition.
    
  • Whether the biodiversity value of the on-site habitat is lower on the date of application (or an earlier date) due to activities ('degradation').
    
• Details about the pre-development biodiversity value:
  
  • The biodiversity value of the site before development, on the date of the application (or an earlier date).
    
  • The completed metric calculation, including the calculations, publication date and version of the biodiversity metric used.
    
  • If using an earlier date, the proposed date and reasons for that.
    
• Information about irreplaceable habitats:
  
  • A description of any irreplaceable habitat on the land, as it exists on the date of application (or an earlier date).
    
  • A plan showing the on-site habitat and any irreplaceable habitat, drawn to scale with north indicated.
    
• Relevant dates:
  
  • Where unauthorised degradation has taken place between 30 January 2020 and the submission of the planning application, the relevant date should be immediately before these activities were carried out.
    

FAQs

How to calculate biodiversity net gain?

Here are the key steps to calculate biodiversity net gain:

1. Use the Statutory Biodiversity Metric or the Small Site Metric tool to assess the biodiversity value of the site:
   • Determine the types of habitats present and their condition.
   • Measure the size/area of each habitat parcel.
   • Enter this information into the metric tool, which will calculate the baseline biodiversity units.
2. Assess the impact of the development:
   • Use the metric tool to calculate the biodiversity units that will be lost due to the development.
3. Plan for biodiversity net gain:
   • Determine what actions are needed to provide at least a 10% increase in biodiversity units compared to the baseline.
   • This may involve creating, restoring or enhancing habitats on-site or off-site.
   • Enter the details of the proposed habitat changes into the metric tool to calculate the new biodiversity units.
4. Create a Biodiversity Net Gain Plan:
   • Document the baseline biodiversity value, the impact of the development, and the planned actions to achieve at least 10% net gain.
   • Include a habitat plan showing the existing and proposed habitats.
5. Use a competent ecologist:
   • For major developments, a qualified ecologist must complete the Statutory Biodiversity Metric.
   • Smaller sites can use the simpler Small Site Metric without an ecologist.

The key is using the standardised metric tools provided by the government to quantify the baseline biodiversity, measure the impact, and demonstrate how the required 10% net gain will be achieved through habitat creation, restoration or enhancement.

What is a biodiversity net gain assessment?

A biodiversity net gain assessment is a process that developers must go through to quantify the impact their project will have on the local biodiversity and habitats. The BNG assessment ensures that development projects are designed to actively improve the natural environment, rather than just minimising their negative impact.
This is done by:

• Measuring the baseline biodiversity value of the site before development.
  
• Calculating the biodiversity units that will be lost or degraded.
• Determining what actions can be taken, either on-site or off-site, to create, restore or enhance habitats in order to achieve a minimum 10% increase in biodiversity units.
• Documenting all of this in a Biodiversity Net Gain Plan.
  

What tool do we use to measure biodiversity?

For large development projects, applicants are required to use an ecologist responsible for using the Statutory Biodiversity Metric tool.

For smaller sites, a professional is not needed. The applicant can use digital tools to complete their Small Site Metric sheet, such as the Joe’s Blooms one. 

Create your free account

What are biodiversity units (BUs)? 

Biodiversity Units quantify the biodiversity value of a piece of land, by measuring the biodiversity loss and gain pre-development. 

To secure 10% BNG uplift pre-development, off-site units can be allocated to the site. These can either be units: 

• generated on the developer’s own land (e.g. in the blue line) 
  
• or from a separate landowner. 

In either case, the Local Planning Authority needs to approve the units, they need to be sustainable for 30 years and registered in the Natural England register.

Read more on biodiversity units

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